U.S. Pat. No. 4,275,118 to Baney et al discloses a coating composition comprising an acidic dispersion of colloidal titania, colloidal silica and hydroxylated silsesquioxane in an alcohol-water medium which produces a hard, abrasion-resistant coating when cured on a plastic surface such as polycarbonate.
U.S. Pat. No. 4,299,746 to Frye discloses an improved silicone resin abrasion resistant coating composition prepared by hydrolyzing an alkyltrialkoxysilane in an aqueous colloidal silica dispersion and adding thereto a small amount of an ultraviolet light absorbing compound such as 2,4-dihydroxybenzophenone to the hydrolysis product.
U.S. Pat. Nos. 4,390,373 and 4,442,168 to White et al disclose a cured, transparent, abrasion resistant coating composition comprising an effective abrasion resisting amount of a colloidal dispersion containing colloidal antimony oxide and colloidal silica in a weight ratio of less than or equal to about 30:70 in a water-alcohol solution of the partial condensate of R (Si(OH).sub.3) wherein R is an organic radical.
U.S. Pat. No. 4,395,461 to Ching discloses a method for improving the weatherability of a polycarbonate substrate by initially treating the surface of the polycarbonate substrate with a solution of a hydrolyzed silylated organic UV screen followed by the application of a curable silicone hardcoat composition onto the treated substrate.
U.S. Pat. No. 4,405,679 to Fujioka et al discloses a coated shaped article of a polycarbonate type resin of improved abrasion resistance comprising a shaped polycarbonate substrate, an undercoat applied and cured on the substrate, and an overcoat applied and cured on the undercoat comprising a hydrolyzate of an epoxy-containing silicon compound, at least one member of the group of hydrolyzates of organic silicon compounds, colloidal silica and organic titania compounds, and a curing catalyst.
U.S. Pat. No. 4,477,499 to Doin et al discloses ultraviolet radiation resistant silicone resin coatings having improved thermoformability and shortened required aging achieved by the addition of a Lewis acid compound to the coating composition.
U.S. Pat. Nos. 4,500,669 and 4,571,365 to Ashlock et al disclose transparent, abrasion resistant coating compositions comprising a colloidal dispersion of a water insoluble dispersant in a water-alcohol solution of the partial condensate of silanol wherein the dispersant comprises metals, alloys, salts, oxides and hydroxides thereof.
U.S. Pat. No. 4,552,936 to Moore discloses a protective coating composition containing a polycaprolactone polyol and an aminoplast derivative applied to a thermoplastic substrate to produce a thermoformable article having abrasion resistance, solvent resistance and weatherability.
European Patent Application No. 851102939 published May 2, 1986 entitled "Carbon-Containing Monolithic Glasses Prepared by a Sol-Gel Process" by Baney et al of Dow Corning Corporation discloses an intermediate which comprises a dispersion of a colloidal metal oxide in a water-alcohol solution of the partial condensate of a silanol having the formula RSi(OH).sub.3, wherein the metal oxide is ZrO.sub.2, SnO.sub.2, ZrSiO.sub.4, B.sub.2 O.sub.3 or La.sub.2 O.sub.3.
Optical quality abrasion resistant coated plastic materials generally require a coating that protects the substrate from the damaging effects of ultraviolet (UV) radiation. Protection from ultraviolet radiation is especially important for polycarbonate, since hydrolytic degradation is apparently accelerated by UV exposure. Conventional UV stabilizers do not impart sufficient protective capacity to abrasion resistant coatings, as sufficient amounts of most typical organic UV absorbers cannot be added to water/alcohol based sol-gel type abrasion resistant coating compositions due to limited solubility and further without adversely affecting hardness and adhesion of the coating. Moreover, typical UV absorbers may gradually become deactivated after prolonged exposure, and also may gradually be leached from the composition.